Grid Coordinate System
In order to record intra-site spatial relationships a fixed series of datums was established at the site. The metal detector survey had determined that targets ceased to be acquired approximately 10 m beyond the ballast mound. Therefore, to allow for undetected features, a 30 m by 40 m grid was superimposed over the wreck site. The grid system also was conceived to readily accept the possibility of additional discoveries of associated material in the Emanuel Point vicinity. To this end, an arbitrary point in deeper water to the south and west of the ballast pile was chosen for a zero northing and zero easting datum from which to superimpose a grid system over the main area of the site and surrounding area. The 30m by 40m grid was aligned with the axis of the ship’s keelson was determined to lie along a bearing of 270 degrees magnetic north. The rectangular control grid was delineated around the site by placing eight primary datum rods into the sand bar. Aligned with the keelson, and the main mast mortise as the midpoint, the grid was laid out by triangulation.
The grid was further subdivided into four equal quadrants. Subdatums were placed in the center of each of the four quadrants for the purpose of acquiring triangulation points in close proximity to features throughout the site. Polypropylene line was then laid to connect the eight primary datums. In conditions of poor underwater visibility, this line functioned as a pathway to the datums, and as a boundary line to contain errant divers. Each datum corresponded to an arbitrary northing and easting value, although the grid was aligned to the ship’s hull remains, rather than a magnetic direction. For example, the southwestern corner of the grid was numbered 100 N and 100 E. Moving northward along the grid, the Northing number increased until reaching the northwestern corner, which was numbered 130 N and 100 E, while the Easting number increased, moving eastward to the southeastern corner, which was 100 N and 140 E. Individual excavation units were numbered according to their position in the grid and were identified by their southwestern corner number, for example, 114 N/131 E.